Plunger switches are widely utilized in many diverse applications including use as safety switches in various motorized devices. For example, U.S. Pat. Nos. 5,424,502, issued Jul. 27, 1993 to Williams, entitled QUICK-INSTALL SEAT SWITCH and assigned to the assignee of the present invention discloses a plunger switch and quick install mounting assembly for mounting the plunger switch on a rigid seat pan of a garden or lawn tractor. The '502 patent is incorporated herein in its entirety by reference. The switch assembly disclosed in the '502 patent is a single pole plunger switch that is a switch with two terminal contacts, the plunger switch electrically coupling or decoupling the two terminals depending upon the plunger or actuator position. The mounting assembly of the '502 patent affixed the plunger switch to the seat pan such that the actuator extends above the seat pan and the switch housing was below the seat pan.
A cover overlies the actuator. When the operator is seated on the seat cushion, the cover is forced downward by the deflection of the seat cushion thereby depressing the actuator from its first undepressed position to a second depressed position. If the switch assembly was a normally closed switch (i.e., the terminals were electrically coupled with the actuator was in its first undepressed position) and the switch assembly terminals were electrically coupled between the tractor engine magneto and an electrical ground of the tractor, the tractor engine would be shut off whenever the operator stepped (or fell) off of the tractor seat. That is, actuator would return to its first undepressed position thereby closing the electrical connection between the magneto and electrical ground resulting in the magneto being grounded out and stalling the engine.
With additional switches and/or relays appropriately mounted and connected, more sophisticated safety functions could be accomplished, for example, shutting off the engine only if the operator was not sitting on the seat and the tractor's mowing blade and/or power take off was engaged. U.S. Pat. No. 5,190,019, issued Mar. 2, 1993 and entitled INTERLOCK CIRCUIT FOR DE-ACTIVATING AN ENGINE, also assigned to the assignee of the present invention discloses such a circuit. The '019 patent is incorporated in its entirety by reference. Once again, a single pole seat mounted safety switch was contemplated.
While the tractor seat pan mounted plunger-type safety switch disclosed in the '502 patent provided a securely mounted switch that was easy to mount, such a switch (and other such prior art seat mounted safety switches) provided only a single circuit (one pole) switch. With the desire for additional operational fail-safe safety functions on lawn and garden tractors and riding lawn mowers such as turning the engine off if the cutting blade is engaged and the tractor is shifted into reverse, there is a need for a safety switch having more than one pole, thereby avoiding the necessity of duplicate switches and/or relays. Further, because of limited mounting room below the seat pan, it is desirable that the switch housing and connector be configured to minimize the height of the assembly extending below the seat pan, that is, along an axis of movement of the actuator. Additionally, it is desirable to prevent an operator from bypassing the operation of the safety functions provided by a seat mounted safety switch by simply disengaging the connector coupled to the switch housing.